Java 自定义适配器中的SetText NullPointerException

自定义适配器类形成一个视图，但在设置列表项的文本时会出现空指针异常

notificationadabter.java

 public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder mViewHolder;
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.row, parent, false);
        mViewHolder = new ViewHolder(convertView);
        convertView.setTag(mViewHolder);
    } else {
        mViewHolder = (ViewHolder) convertView.getTag();

    }

    MessageModel currentListData = getItem(position);

   Log.i(tag,mViewHolder.source.getText().toString());

    try {
        mViewHolder.name.setText(currentListData.getName());
        mViewHolder.source.setText(currentListData.getSource());
        Log.i(tag, currentListData.getName());
        mViewHolder.destination.setText(currentListData.getDestination());
        mViewHolder.message.setText(currentListData.getMessage());
        mViewHolder.time.setText(currentListData.getTime());
    }
    catch(Exception e){}//Log.i(tag,"4");
    if(convertView==null)
        Log.i(tag,"null");
    else
        Log.i(tag,"not null");
    return convertView;
}

gettext也适用于上面的视图，但setText提供NPE。仔细检查所有xml文件是否有任何打字错误

    public class ViewHolder {
    TextView name;
    TextView source;
    TextView destination;
    TextView message;
    TextView time;
    public ViewHolder(View item) {
        name=(TextView) item.findViewById(R.id.lblname);
        destination=(TextView) item.findViewById(R.id.lblDestination);
        message=(TextView) item.findViewById(R.id.lblSCustMsg);
        time=(TextView) item.findViewById(R.id.lblSTime);
        source=(TextView) item.findViewById(R.id.lblSSource);
    }
}

数据源模型

public class MessageModel {
String source,destination,custmsg,time,name;
public MessageModel(String source,
                    String destination,String custmsg,
                    String time,String name)
{
    this.source=source;
    this.destination=destination;
    this.custmsg=custmsg;
    this.time=time;
    this.name=name;
}
public String getName()
{
    return name;
}
public String getSource()
{
    return source;
}
public String getTime()
{
    return time;
}
public String getMessage()
{
    return custmsg;
}
public String getDestination()
{
    return destination}} 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/lblSName"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSTime"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSSource"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSDestination"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSCustMsg"
    android:text="item" />

调试

4-17 23:47:19.378 23874-23874/com.example.abc.myapplication E/AndroidRuntime:FATAL EXCEPTION: main
                                                                         java.lang.NullPointerException
                                                                               at com.example.abc.myapplication.NotificationAdapter.getView(NotificationAdapter.java:76)
                                                                               at android.widget.AbsListView.obtainView(AbsListView.java:2340)
                                                                               at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
                                                                               at android.widget.ListView.onMeasure(ListView.java:1162)
                                                                               at android.view.View.measure(View.java:15264)
                                                                               at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
                                                                               at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
                                                                               at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1038)
                                                                               at android.widget.LinearLayout.onMeasure(LinearLayout.java:576)
                                                                               at android.view.View.measure(View.java:15264)
                                                                               at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
                                                                               at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
                                                                               at android.view.View.measure(View.java:15264)
                                                                               at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
                                                                               at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
                                                                               at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
                                                                               at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
                                                                               at android.view.View.measure(View.java:15264)
                                                                               at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
                                                                               at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
                                                                               at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2161)
                                                                               at android.view.View.measure(View.java:15264)
                                                                               at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2131)
                                                                               at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1242)
                                                                               at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1435)
                                                                               at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1127)
                                                                               at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4609)
                                                                               at android.view.Choreographer$CallbackRecord.run(Choreographer.java:747)
                                                                               at android.view.Choreographer.doCallbacks(Choreographer.java:567)
                                                                               at android.view.Choreographer.doFrame(Choreographer.java:536)
                                                                               at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:733)
                                                                               at android.os.Handler.handleCallback(Handler.java:615)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:92)
                                                                               at android.os.Looper.loop(Looper.java:153)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:4987)
                                                                               at java.lang.reflect.Method.invokeNative(Native Method)
                                                                               at java.lang.reflect.Method.invoke(Method.java:511)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
                                                                               at dalvik.system.NativeStart.main(Native Method)

row.xml

public class MessageModel {
String source,destination,custmsg,time,name;
public MessageModel(String source,
                    String destination,String custmsg,
                    String time,String name)
{
    this.source=source;
    this.destination=destination;
    this.custmsg=custmsg;
    this.time=time;
    this.name=name;
}
public String getName()
{
    return name;
}
public String getSource()
{
    return source;
}
public String getTime()
{
    return time;
}
public String getMessage()
{
    return custmsg;
}
public String getDestination()
{
    return destination}} 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/lblSName"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSTime"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSSource"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSDestination"
    android:text="item" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:id="@+id/lblSCustMsg"
    android:text="item" />

换衣服

name=(TextView) item.findViewById(R.id.lblname);

进入

---

可能currentListData为空，因此在setText之前添加

if（currentListData！=null）

另外，

findViewById（）中的名称和目的地不正确。

你必须改变：

name=(TextView) item.findViewById(R.id.lblname);
into：
name=(TextView) item.findViewById(R.id.lblSName);

destination(TextView)item.findViewById(R.id.lblDestination);
into：
destination=(TextView) item.findViewById(R.id.lblSDestination);

---

如果我告诉您

currentListData

为空会怎样？是否可能

currentListData

为

null

，即

getItem（）

方法可以返回

null

值？如果是这样，这可能解释了NPE.currentlistData.getName（）。打印为调试消息您是否确定所有这些

TextView

s都在

行

布局中？

lblname

和

lbldestinion

不在

行

布局中。它们应该是

ViewHolder

构造函数中的

lblSName

和

lblSDestination

。以及

lbldestinition